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How To Locate The Primary Winding Of Flyback Transformer

By on November 24, 2008

flyback schematic

Got a question from ERG member:

Can the Blue Ring Tester that I purchased from you be able to test the TV Flyback Transformers?

Jestine- Yes you can

And what If I do not have some of the TV schematic diagrams, how should I identify which pins in pair. Meaning to say pin No.?  & pin No.? are related for testing.

Jestine- Check for the flyback pin that goes to the collector pin of HOT and the B+ pin (supply from power supply). That is the primary winding of flyback transformer.

If you are repairing the CRT Monitor then you have to find out from center pin of the B+ FET that goes through a Diode  (ultra fast recovery diode) and then to the flyback pin. Another pin was from the collector of HOT. Both the pins is the primary winding of the flyback transformer. Try practice to find these two pins because i came across quite a number of technicians could not trace these pins. The primary winding is important if you are in the CRT TV/Monitor repair because a shorted/ partial shorted winding could cause the equipment to shutdown, low power, power blink or even blow up the HOT. If you come across a shorted HOT please make sure you test this primary winding before you put in a new HOT otherwise if the primary winding have problem, it may takes a split of seconds to kill the new HOT.

Again, it come back to the important of using flyback tester/Blue Ring Tester to find out the bad winding. Without the tester, surely it would take you a longer time to troubleshoot the problem that related to shorted primary winding in Flyback transformer.



  1. russ

    February 22, 2011 at 5:09 am

    If I don't have a schematic how do I know where the B plus is? Are there some more clues you can give? Are they ever at the same pin number, or do they ever read a particular ohm? Can you show me some exambles on a flyback and on a schematic?
    Thank you

  2. admin

    February 22, 2011 at 8:44 am

    HI Russ,

    For a TV, just trace the 110 vdc line of the power supply and it will lead you to the B+ pin of flyback.


  3. lito mendoza

    September 28, 2011 at 8:42 am


    aside from the 2 pins of the primary winding in the lopt/fbt transformers, what are the functions of the remaining pins? just in case the primary winding of lopt/fbt is ok, will the remaining pins of the transformers be the cause of the tv/monitor shutting down?

    thanks a lot,


  4. admin

    September 29, 2011 at 8:39 am

    Hi Lito,

    Try this link:

    usually the secaondary winding will not cause shutdown unless it is shorted.


  5. worku

    October 17, 2011 at 9:32 am

    how to check the fly back ,it is normal or not normal

  6. admin

    October 18, 2011 at 3:25 am

    HI Worku,

    Try this link:


  7. jojogreg

    September 5, 2012 at 11:11 pm

    hi jestine,
    Can i measure the primary winding of the flyback transformer using analog or digital multimeter?How can i know that the primary winding is defective?Is it shorted or a zero resistance?What is the right range setting in   the analog meter if possible..

    • Jestine Yong

      September 6, 2012 at 3:47 am

      Hi JOJO,

      You can't use analog/digital meter to check on the primary winding because a shorted winding the meter will still show good reading (Ohms value). You need Blue Ring Tester to locate shorted winding in flyback transformer.


  8. boy ukel

    November 15, 2013 at 7:46 am

    halo mr jestine...i got a crt tv that have a red led like standby..when i check the 100uf 160v on secondary has blown...i replace it and the cap become hot and looks like gonna explode i check all the sorrounding component..but nothing shorted...check the HOT....also good...check all the component around flyback..also no luck finding bad component....can mr jestine help me??

    • Jestine Yong

      November 15, 2013 at 10:37 am

      Hi Boy,

      Try check the 100uf 160 volt cap again before it blow to see how many volt across it.


  9. Denis Luleti

    December 17, 2013 at 3:22 pm

    Thanks a lot i finally located the primary windings of a flyback it has always been a headache for me but thanks to Jestine's recommedations i easily got it.

  10. Vali kabini

    October 7, 2016 at 8:31 pm

    What is the vertical and horizontal sections of the CRT TV. Secondly, how can I identify the names of TV ICS and their images and their voltages? Pks help!!!

    • Jestine Yong

      October 10, 2016 at 3:17 pm

      HI Vali,

      I suggest that you get Humphrey's ebook that has all the answers you need:


  11. Md s islam

    January 24, 2017 at 3:54 pm

    hi sir i get an problem the CRT TV be have 180 voltage in CRT board but when turn on the tv have green and blue but red is com too later, so sir please you give me an suggestions

    • Jestine Yong

      January 30, 2017 at 1:40 pm

      Hi md Islam,

      It could be dues to weak picture tube or the red circuit in the CRT board have bad components.


  12. saeed

    September 13, 2017 at 4:31 am

    Hello . What is the hi voltage number in the image above?

    • Jestine Yong

      September 14, 2017 at 8:23 pm

      Hi Saeed,

      I no longer keep this flyback thus would not know what is the part number. That post already been posted 9 years ago.


  13. Mevias

    December 16, 2018 at 4:34 pm

    Hi,how are you doing?longtime since I sent you a mail,my tv went off,no power light,no light on the neck picture tube.what could be the problem.thank you good day.

    • Jestine Yong

      December 17, 2018 at 9:19 am

      Hi Mevias,
      I'm fine thanks. Your TV problem could be in the power supply fault. Have you checked the power supply section components? Have you checked if there is dc supply to the power IC?



    September 5, 2019 at 11:05 pm

    Thanks Mr. yong your article make me feel as one of the professionals in locating the primary windings of the flyback transformer. cause this have given me problems over the years each time I cane across new design of the flyback transformer.

  15. Wamunyima Biemba Patrick

    March 22, 2021 at 11:04 pm

    Hi jestine what caused all components to short/open on the board eg the HOT, resistors, and all Capacitors on the secondary side of 29 inch Nikura crt tv. Is it a board which needs to be replaced, what is your advise?

    • Jestine Yong

      March 25, 2021 at 8:36 pm

      Hi Wamunyima,

      It is impossible for all components to short and open in a circuit board. Usually only couple of components that can have problem. Without hands on assessment on that TV I can't tell which components to check or to replace.


  16. Micheal Rodgers

    March 28, 2023 at 6:39 pm

    Hello Mr jestine yong l would like to ask how do l find the cold ground on the secondary side of an smps?

    • Jestine Yong

      March 30, 2023 at 8:52 pm

      Hi Michael,
      The cold ground is your equipment chassis ground. Or you can look for the negative lead of the filter cap in the secondary side of your switch mode power supply. That negative lead of the filter capacitor is the cold ground.



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